1. Field
This disclosure relates to magnetic resonance imaging (MRI) methods and apparatuses that effectively differentiate tissues of a subject undergoing MRI in order to separate images of the tissues of the subject.
2. Description of Related Art
Magnetic resonance imaging (MRI) is a technique that exposes atomic nuclei to a magnetic field and obtains an image by using information obtained through resonance of the atomic nuclei. Resonance is a phenomenon where when a specific high-frequency wave is incident on atomic nuclei magnetized by an external magnetic field, the atomic nuclei absorb the high-frequency wave and are excited from a low energy state to a high-energy state. Atomic nuclei have resonance frequencies that vary according to types of the atomic nuclei, and resonance is affected by the strength of an external magnetic field. A number of different atomic nuclei exist in a human body, and hydrogen nuclei are generally used in MRI.
In particular, in MRI, various methods of differentiating tissues constituting a human body and removing a signal of a specific tissue have been studied. Examples include a method using chemical-shift selective saturation (CHESS) imaging and a method using Dixon water/fat imaging. The method using CHESS imaging uses a difference in a resonance frequency due to a difference in a chemical shift between two tissues in order to differentiate the two tissues. The method using Dixon water/fat imaging uses a difference in an image phase due to a difference in a resonance frequency between two tissues. In this case, since the chemical shift, the resonance frequency, and the image phase are proportional to one another, it is difficult for the method using CHESS imaging and the method using Dixon water/fat imaging to differentiate the two tissues unless there is a sufficient difference in a chemical shift and a resonance frequency between the two tissues.